ETC Crime Scene Processing 3 — Questions and Answers
Question 1: The 'Locard Exchange Principle' is most directly relevant to crime scene processing because it states that:
- Every crime scene must be photographed before touching anything
- When two objects contact each other, trace material is exchanged (Correct answer)
- Evidence must be collected in order of fragility
- Chain of custody must be maintained at all times
Correct answer: When two objects contact each other, trace material is exchanged
Locard's principle holds that every contact between a person and a scene results in the transfer of trace material in both directions.
Question 2: A technician is casting a tire track in soft soil. Which material is most commonly used?
- Plaster of Paris
- Dental stone (die stone) (Correct answer)
- Silicone rubber
- Liquid latex
Correct answer: Dental stone (die stone)
Dental stone is preferred over plaster of Paris for tire and shoe impression casting because it is harder, more durable, and captures finer detail.
Question 3: Which action would MOST compromise the integrity of digital evidence found on a computer at a crime scene?
- Photographing the screen before shutdown
- Powering on the computer to check its contents (Correct answer)
- Documenting the cable connections
- Placing the device in an anti-static bag
Correct answer: Powering on the computer to check its contents
Powering on a computer can alter timestamps, overwrite temporary files, and activate encryption, destroying critical digital evidence.
Question 4: At an outdoor homicide scene, what environmental factor poses the greatest threat to trace DNA evidence?
- Wind direction
- UV radiation and moisture (Correct answer)
- Ambient noise levels
- Soil pH
Correct answer: UV radiation and moisture
UV radiation breaks down DNA strands and moisture accelerates microbial degradation, making them the primary environmental threats to trace DNA.
Question 5: When should a crime scene log (scene entry/exit record) be initiated?
- After the lead investigator arrives
- After the scene has been fully photographed
- Immediately upon securing the scene (Correct answer)
- Before the medical examiner is notified
Correct answer: Immediately upon securing the scene
The scene log must begin as soon as the scene is secured to record every person who enters or exits from that point forward.
Question 6: A bloodstain with a circular shape and smooth edges most likely indicates the blood fell at approximately what angle?
- 15 degrees
- 45 degrees
- 90 degrees (perpendicular) (Correct answer)
- 60 degrees
Correct answer: 90 degrees (perpendicular)
Blood falling at 90 degrees to a surface produces a circular stain with smooth, even edges because there is no angular distortion.
Question 7: Which step is performed LAST when processing a latent fingerprint with cyanoacrylate (super glue) fuming?
- Sealing the item in a fuming chamber
- Photographing the developed prints (Correct answer)
- Applying dye stain to enhance contrast
- Heating the cyanoacrylate source
Correct answer: Photographing the developed prints
After cyanoacrylate fuming develops the print and optional dye staining enhances contrast, the final step is photography to document the result.
ETC Crime Scene Processing 3
The 'Locard Exchange Principle' is most directly relevant to crime scene processing because it states that: